UV Curable UV500

HumiSeal® UV500 is a high solids UV dual cure elastomeric acrylate conformal coating. HumiSeal® UV500 exhibits excellent flexibility, moisture resistance and electrical insulation properties as well as good chemical resistance.

HumiSeal® UV500 has been specifically developed to:

  • Cure tack-free with microwave or arc UV
  • Have a secondary cue mechanism that will fully cure any unexposed areas of the coating within 7 days at ambient
  • Have a higher flexibility compared with other UV curable conformal coatings, giving improved performance in thermal cycling
  • Fluoresce under UV light to allow coating
  • Be applied by all selective coating
  • Have excellent chemical and moisture

HumiSeal® UV500 meets the following standards:

  • IEC 60664-3
  • Compliant to REACH, RoHS Directive EU 2015/863
  • Compliant with China RoHS 2
  • Compliant to China Standard GB30981-2020
  • Recognized under UL File Number E105698

Properties of HumiSeal®UV500 Liquid Coating

Density 1.0 to 1.1 g/cm3
Minimum Solids Content, % by weight 98%
Viscosity at 25ºC 275 to 375 centipoise
Shelf Life at Room Temperature, DOM  9 Months
Recommended UV Cure See Curing Below

* Unless otherwise specified on material packaging

Properties of HumiSeal®UV500 Cured Coating

Coating Thickness, as recommended by IPC guidelines 25 – 125 microns
Coating Thickness, as recommended for application 75 – 130 microns
Time to reach optimum properties 7 days after UV cure
Glass Transition Temperature – DSC -43°C
Coefficient of Thermal Expansion – TMA 137ppm/°C Below Tg 311ppm/°C Above Tg
Modulus – DMA 0.4MPa @ 25°C
 Dielectric Withstand Voltage, per MIL-I-46058C  > 1500 V
 Surface Insulation Resistance (per IPC J-STD-004 (mod.)  8.9 log 10 ohms
Moisture Insulation Resistance, per MIL-I-46058C 1.6 x 1010 ohms
Flammability per UL94 V-0
Fungus Resistance, per IPC-TM-650 Pass
Thermal Conductivity 3.07
Insulation Resistance, per MIL-I-46058C 4.5 x 1011 ohms
Surface Resistivity per ASTM D-257 2.0 x 1011 ohms
Volume Resistivity per ASTM D-257 8.0 x 1012 ohm.cm

Application of HumiSeal®UV500

Conformal coatings can be successfully applied to substrates that have been cleaned prior to coating and also to substrates assembled with low residue, “no clean” assembly materials. Users should perform adequate testing to confirm compatibility between the conformal coating and their particular assembly materials, process conditions and cleanliness level. Please contact HumiSeal® for additional information.


HumiSeal® UV500 can be applied via standard selective coating equipment or by conventional hand spray equipment. The source air used for spraying must be dry (a dry inert gas (nitrogen or argon) is highly recommended) to prevent premature curing of the secondary cure mechanism. The spraying should be done with adequate ventilation so that the vapor and mist are carried away from the operator.


HumiSeal® UV500 may be applied by brush for rework or touch up only. Brush must be cleaned with solvent promptly after use.


HumiSeal® UV500 is a highly crosslinked coating. In order to achieve maximum crosslinking density, the product must be exposed to the correct spectral output. Humiseal has modelled the performance of UV500 using Arc and Microwave based UV curing equipment. The table below outlines the required dosage and irradiance values necessary to render HumiSeal® UV500 tack free post UV exposure with both equipment types. Minimum figures should provide a tack free surface. The maximum recommendation represents highest tested values by Humiseal. The cure recommendations may change as curing technology develops.


Dose J/cm2* Irradiance W/cm2*
Min Arc System 1.5 1.5 0.40 0.50 0.50 0.10
Min Microwave System 2.0 2.0 0.40 0.70 0.70 0.15
Max Arc System 2.80 2.70 0.80 0.90 0.80 0.20
Max Microwave System 3.00 3.00 0.60 1.15 0.25

*Values measured with a Powerpuck II UV radiometer

Heat is also an important component with UV cure, and different systems produce different heat outputs. Higher heat levels allow UV cure at lower dose/irradiance levels. Consequently, Humiseal recommend that curing is discussed with HumiSeal® Technical staff to ensure the exact customer process being used will meet the coating cure requirements. After UV exposure and return to room temperature the coating should be tack free.

HumiSeal® UV500 contains a reliable secondary moisture cure mechanism which will cure any shadow areas on the assembly within 7 days at ambient moisture.

HumiSeal® UV500 was designed to be cured using a microwave UV oven equipped with an “H” style bulb. Arc systems can cure HumiSeal® UV500 however care must be taken during the equipment selection process to ensure minimum dosage and irradiance values obtained will properly cure the coating. Because of the variations possible in curing equipment type and configuration, it is strongly recommended that you contact HumiSeal Technical Support to discuss your equipment and process in detail.

Clean Up

To flush equipment and clean uncured HumiSeal® UV500, non-alcohol based solvents should be used. HumiSeal® Thinner 521 or Thinner 521EU is recommended.


HumiSeal® UV500 is a highly crosslinked UV cured coating. The cured film has a high degree of environmental and chemical resistance and will be more difficult to remove than traditional conformal coatings. Thermal displacement and mechanical abrasion are suitable options for rework of HumiSeal® UV500. Humiseal Stripper 1072 and 1100 can be used effectively to remove UV500 after full moisture cure.


HumiSeal® UV500 is photosensitive. The product should not be exposed to direct sunlight or full spectrum fluorescent lighting. HumiSeal® UV500 should be stored cool below 20°C, to maximize shelf life. Prior to use, allow the product to equilibrate for 24 hours at room temperature. HumiSeal® UV500 is a moisture curing material and care should be taken to protect process vessels and partial containers from moisture.

Partial containers must be purged with a dry, inert gas such as dry air, nitrogen or argon before closure, otherwise premature polymerization by atmospheric moisture will occur.


Application of HumiSeal® Conformal Coatings should be carried out in accordance with local and National Health and Safety regulations.

Use only in well-ventilated areas to avoid inhalation of vapours or spray.

Avoid contact with skin and eyes. Consult SDS prior to use.